High chambered coke oven structure



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Sheei L. G. TUCKER ET AL HIGH CHAMBERED COKE OVEN STRUCTURE Dec. 31, 1968 V Filed $ept. 1, 1964 United States Patent 3,419,475 HIGH CHAMBERED COKE OVEN STRUCTURE Linwood G. Tucker, Pittsburgh, and Elliott Preston, Glenshaw, Pa., assignors to Koppers Company, Inc., a corporation of Delaware Filed Sept. 1, 1964, Ser. No. 393,512 5 Claims. (Cl. 202-143) ABSTRACT OF THE DISCLOSURE This disclosure relates to a hairpin flue type high chambered coke oven structure. The heating chambers have a plurality of aligned vertical flues with high and low burners in each flue. The flues are arranged in interconnected pairs for flow of combustion gas from one flue into the adjacent interconnected flue through an opening in the partition wall separating the interconnected flues. Division walls separate the pairs of interconnected flues from adjacent pairs of interconnected flues. There are vertical supply passageways extending upwardly to each high and low burner from a gas distribution system located below the base of the flues that are arranged to supply fuel gas to the high and low burners of one of the interconnected flues. There are transverse passageways connecting the vertical supply passageways so that the first portion of the waste combustion gas is admixed with the fuel gas being supplied to one of the burners of the interconnected pair of flues and a second portion of the waste combustion gas is admixed with the fuel gas being supplied to one of the burners of a separate non-connected flue on the opposite side of the division wall. With this arrangement, waste combustion gas is circulated between flues separated by a division wall.

This invention relates to improvements in a high chambered horizontal regenerative coke oven and more particularly to a hairpin flue type high chambered coke oven that includes high and low burners and means for connecting the high and low burners of adjacent flues for the admixture of waste combustion gas with rich fuel gas supplied to the high and low burners.

In the design and construction of horizontal retort coke ovens, one of the primary objectives in recent years has been to increase oven capacity without adversely affecting the quality of the coke produced therein. To attain this objective the height of the coke chamber has been increased and high and low burners are utilized in the combustion flue to provide heat to the coking chambers. It is desirable that combustion at the high and low burners be suchthat the heat is distributed uniformly through the heating walls to the coal in the coking chambers of increased height. It is, therefore, necessary to obtain a reasonably uniform distribution of temperature from the bottom to the top of the combustion flue. One method of obtaining this temperature distribution is to admix a portion of the gaseous products of combustion commonly referred to as waste gas with the fuel gas at or near the base of the flues. The admixture of waste gas and fuel gas provides anvelongated flame that supplies radiant heat to a greater part of the flues in which combustion progresses, thus assuring a uniform temperature from the bottom to the top of the flues and to the coal charge heated in the adjacent chambers.

It has also been found where a rich fuel gas is conveyed through the riser passages to the high burners, the gas is subjected to elevated temperatures from the heat generated by the burning of the fuel gas at the low level burner. This elevated temperature causes thermal decomposition of the rich fuel gas in the vertical riser passages and deposits a carbonaceous residuum on the riser passage walls. This carbonaceous residuum causes a serious oper- 3,419,475 Patented Dec. 31, 1968 ICC ating problem by clogging the riser passages so that fuel gas cannot flow to the high level burners. It has been discovered by admixing a portion of the waste combustion gas with the rich fuel gas that the admixture may be subjected to high temperatures without substantial thermal decomposition of the fuel gas and without substantial deposit of the carbonaceous residuum on the walls of the riser passages.

In a hairpin flue type oven where adjacent flues are interconnected and combustion takes place in the on flue, the combustion gases from the on flue flow downwardly in the adjacent off flue. The waste combustion gases flowing downwardly in the off flue provide a readily available source of diluent gas for the rich fuel gas flowing upwardly through the riser passages to the various burners in adjacent on flues. Where the hairpin flue type regenerative oven has an underjet type of fuel gas supply, the rich fuel gas flows upwardly through the gas riser conduits or passageways from beneath the regenerators to the base of the flues. The rich fuel gas flowing upwardly through the gas riser passages is also subjected to the elevated temperatures of the regenerator brickwork, and admixing at least a portion of the waste combustion gases with the rich fuel gas at a location beneath the regenerators minimizes the thermal decomposition of the rich fuel gas in the gas riser conduits in the regenerator brickwork.

The present invention is directed to a high chambered horizontal coke oven of the hairpin flue type wherein the fuel gas is supplied to the flues through gas riser conduits or passages from a supply source positioned beneath the regenerators. A gas recirculation means is provided beneath the regenerators that connects the vertical gas riser conduits of adjacent flues. A portion of the waste gas flowing downwardly through the off flues is conveyed downwardly through the upwardly extending fuel supply passages to the recirculation means where it is admixed with the fuel gas flowing upwardly through the vertical fuel supply passageways in adjacent on flues. The admixture of waste combustion gas and rich fuel gas then flows upwardly through the vertical fuel supply passages in the on flues to the respective burners. Another embodiment of the invention includes a means to recirculate waste combustion gas from the off flue to the on flue.

Accordingly, the principal feature of this invention is to provide a hairpin flue type high chambered coke oven with high and low burners and a means for admixing a portion of the waste combustion gases with the fuel gas so that an admixture of rich fuel gas and waste combustion gas is conveyed through the vertical fuel supply passages to the high and low burners of the on flue.

Another feature of this invention is to provide a hairpin type flue regenerative coke oven wherein combustion at both the high and low burners provides a substantially uniform temperature throughout the length of the flue.

Another feature of this invention is to provide an improved means for admixing waste combustion gas with rich fuel gas beneath the regenerators so that both the high and low burners of the on flues are supplied with an admixture of rich fuel gas and waste combustion gas.

Another feature of this invention is to provide a means for recirculating a portion of the waste gas from the off flue to the on flue.

This invention comprises the new and improved construction and combination of parts and their operating relation to each which will be described more fully hereinafter and the novelty of which will be particularly pointed out and distinctly claimed.

In the accompanying drawings to be taken as part of the specification, there is fully and clearly shown two embodiments of this invention, in which drawings:

FIGURE 1 is a crosswise vertical section through a coke oven battery embodying features of the present invention. The battery comprises coke ovens wherein the low and high level burners are supplied with fuel gas by a so-called underjet principle. The section AA is taken along the lines AA of FIGURE 2 and is taken longitudinally through a heating wall of the coke oven; the section B-B is taken along the lines BB of FIGURE 2 and through a coking chamber in a coke oven battery.

FIGURE 2 is a vertical section in elevation taken longitudinally of the coke oven battery and along the line CC of FIGURE 1.

FIGURE 3 is a schematic gas flow diagram similar to section AA of FIGURE 1 and illustrating the recirculation of a portion of the waste gases to adjacent on flues.

FIGURE 4 is a view similar to FIGURE 1 illustrating another embodiment of this invention.

FIGURE 5 is a schematic representation similar to FIGURE 3 illustrating a schematic gas flow diagram of the embodiment of FIGURE 4.

Referring to the drawings and particularly to FIG- URES l and 2, there is illustrated a coke oven battery generally designated by the numeral that has a plurality of heating walls 12 and a plurality of intermediate coking chambers 14. The heating walls 12 form side walls for the respective coking chambers therebetween and form heating chambers to supply heat to the coking chambers. The heating walls 12 are supported by regenerator pillar walls 16 positioned therebeneath. The pillar walls 16 extend crosswise of the coke oven battery 10 and lengthwise of the coking chambers 14.

The coke oven battery 10 has a base portion 18 that supports the pillar walls 16 and the coking chambers and heating chambers thereabove. The heating walls 12 have a plurality of interconnected vertical hairpin type flues 20 and 22 that are connected by a crossover passageway 24. Beneath the coking chambers 14 there are a plurality of crosswise regenerators 26 that have division walls 28 therebetween. There are associated with each of the regenerators a pair of sole fiues 30 which are connected by passages 32 to the regenerator thereabove. The regenerators 26 are connected to the flues by passages 33 so that waste combustion gas is conveyed from the 0fi" flues downwardly through passages 33 to certain of the regenerators 26 and thence through passages 32 to the horizontal sole flues 30. The other sole flues are arranged to be connected to a source of combustion air to supply the respective regenerators and on flues with heated combustion air. Suitable control means is provided for reversing the direction of flow through the regenerators and for alternating between adjacent flues as on flues or off flues.

For convenience, pairs of interconnected flues will be designated with a common letter suflix, such as interconnected flues 20A and 22A and adjacent interconnected fiues 20B and 228. The interconnected flues 20 and 22 have a partition wall 34 therebetween that terminates in a top portion 36 positioned below the top portion 38 of the heating chambers to provide a passageway 24 therebetween. Between adjacent pairs of flues there is a transverse division wall 40 that separates the pairs of flues from each other so that the combustion gas flowing upwardly through the flue 20 is conveyed downardly through the adjacent flue 22. The pairs of fiues 20 and 22 are arranged crosswise of the coke oven battery 10, as is schematically illustrated in FIGURE 3.

The partition wall 34 has a vertical passageway 42 opening into the flue 22 above the flue base portion 44 and forms a gas port 46 for the high level burner in the flue 22. The division wall 40 has a similar vertical passageway 48 that terminates in a gas port 50 for the high level burner in the flue 20. The vertical passageways 42 and 48 extend downwardly through the masonry between the heating chamber and the regenerator chamber and through the pillar walls 16 below the base 18. Both the flues 20 and 22 have openings 52 and 54 in their base portion 44 which form gas ports for the low level burners in each of the fiues. The openings 46 and 50 will be referred to as the high level burners in flues 22 and 20 and openings 52 and 54 will be referred to as the low level burners in flues 20 and 22. There are provided fuel supply passageways 56 and 58 connected to openings 52 and 54 that extend downwardly through the masonry between the base of the fiues 44 and the regenerator chambers, and through the pillar walls 16 and coke oven base portion 18. Thus, vertical passageway 56 supplies fuel gas to the low level burner 52 in the end flue 20 and the vertical passageways 42 and 58 supply fuel gas to the high and low level burners 46 and 54 in the flue 22A. The passageway 42 is interconnected to passageway 56 through a horizontal connecting passageway 60 beneath the regenerators 26. Similarly, the passageway 58 of flue 22 is connected to the passageway 48 for the adjacent flue 203 by a horizontal connecting passageway 62. Similarly, vertical passageway 56 that supplies fuel gas to the low burner 52 of flue 20B is connected to the vertical passageway 42 that supplies fuel gas to the high burner 46 in flue 22B by horizontal passageway 64. The adjacent vertical passageway 58 that supplies fuel gas to the low burner 54 in flue 22B is connected to vertical passageway 48 that supplies fuel gas to the high level burner 46 through horizontal passageway 62. The respective passageways, 48, 56, 42 and 58 are connected to a common header or conduit 68 positioned below the oven base 18. Suitable valve means are arranged to provide for the flow of rich fuel gas from the horizontal header 68 to certain of the vertical passageways depending on whether the flues 20 are the on flues, or the flues 22 are the on fiues in which combustion is to taken place.

As is indicated by the directional arrows in FIGURES l and 3, the fiues 20 are the on fiues and the valving provides upward flow of fuel gas from the header 68 through all of the passageways designated 56 and 48. Suitable nozzles 70 are positioned in the respective passages to control the velocity of fuel gas flowing therethrough. Because of the horizontal connecting conduits 60, 62 and 64, the vertical fuel supply conduits 42 and 58 in fiues 22A and 22B serve as waste gas conduits to convey a portion of the waste combustion gases downwardly therethrough from the flues 22A and 22B. The waste gas conveyed downwardly through conduit 42 of flue 22A flows horizontally through connecting conduit 60 and is admixed with the rich fuel gas flowing upwardly through fuel supply conduit 56 that supplies fuel gas to the low level burner 52 in flue 20A. Similarly, the waste combustion gas from flue 22A flows downwardly through conduit 58 to the horizontal connecting conduit 62 where it is admixed with the rich fuel gas flowing upwardly through the fuel supply conduit 48 that supplies fuel gas to the high level burner 50 in the flue 208. The next adjacent pair of vertical fuel supply passageways that serve as conduits for waste combustion gas in FIG- URE l are conduits 42 and 58 that have their upper portions terminate in flue 22B. The waste gas that is conveyed downwardly through conduit 42 from flue 22B flows horizontally through connecting conduit 64 to the vertical fuel supply conduit 56 where it is admixed with the rich fuel gas supplied to the low level burner 52 in conduit 20B. The waste gas flowing downwardly through conduit 58 from flue 22B flows horizontally through connecting conduit 62 where it is admixed with the rich fuel gas flowing upwardly through conduit 48 to the high level burner 46 in flue 20C. The conduit arrangement for the remaining fiues is repetitive, as is illustrated in FIGURE 3, so that the waste gas conveyed downwardly from the high level burner in the off flue through conduit 42 is admixed with the rich fuel gas supplied through the vertical conduit 56 to the low level burner 52 in the adjacent flue associated therewith. The waste gas conveyed downwardly through the vertical fuel supply conduit 58 from the low level burner 54 in the off flue is admixed with the rich fuel gas flowing upwardly through the supply conduit 48 to the high level burner of the on flue in the adjacent pair of flues.

The schematic flow diagram FIGURE 3 clearly illustrates that the plurality of vertical passageways 58 and 48 are connected by a horizontal passageway 62. Similarly, vertical passageways 56 and 42 are connected by horizontal passageway 64. The horizontal passageway 64 supplies waste combustion gas through the high burner opening in the off flue to the vertical passageway that supplies the fuel gas to the low bu-rner in the adjacent interconnected on flue. The horizontal connecting passageway 62 supplies waste combustion gas through the low burner opening in an off flue to the supply passageway for the high burner in an on flue of the adjacent pair of interconnected flues. Upon reversal of the system, the direction of flow of both the fuel gas and waste gas through the vertical passageways 56, 42, 52, 48 and the horizontal passageways 60, 62, and 64, is reversed so that the previously indicated on flues are now the off flues and the previously indicated off flues are now the on flues. Upon reversal, the waste combustion gas is admixed in a similar manner with the fuel gas supplied to the high and low level burners of the newly designated on flues.

FIGURES 4 and 5 illustrate another embodiment of this invention wherein similar numerals, increased by 100, will be used to indicate similar structure. The division walls 140 have pairs of vertical passageways 142 and 148 on opposite sides thereof that terminate in high level burners 146 and 150 in flues 122A and 120B respectively. The partition walls 134 do not have vertical passageways associated therewith as illustrated in the embodiment of FIGURES 1-3. The remaining vertical passageways supplying fuel gas to the respective high and low level burners are substantially the same as the vertical supply passageways of FIGURES 1-3. The horizontal passageways 160, 162 and 164 are similar to passageways 60, 62 and 64 of FIGURES 1-3. With this arrangement the fuel gas is supplied to the low and high level burners of the on flues through the vertical passageways and portions of the waste combustion gas are withdrawn from the on flues through the fuel supply passageways therein and admixed with the fuel gas supplied to the high and low burners in the on flues.

Each of the partition walls 134 separating the on and off flues of interconnected pairs of flues has a horizontal passageway 176 therethrough adjacent to the flue base portion 144. The horizontal passageways 176 provide a means for recirculating a portion of the waste combustion gas that flows downwardly through the off flue. The waste combustion gas recirculated through the passageways 176 in the partition walls 134 is admixed with the combustion air supplied to the on flues through the passageways 133. The waste combustion gas provides an inert diluent .for the combustion air which enhances the combustion characteristics of the flames at the low and high level burners.

According to the provisions of the patent statutes, the principle, preferred construction, and mode of operation of the invention have been explained, and what is now considered to represent its best embodiments has been illustrated and described. However, it should be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically illustrated and described.

We claim:

1. In a hairpin flue type high chambered horizontal coking retort oven a combination of heating elements therefor to provide uniform heating for the coking chambers comprising:

a plurality of elongated heating chambers arranged in alternating relation with elongated coking chambers, said heating chambers each having a plurality of vertical combustion flues arranged side by side and in a row, each of said flues having high and low positioned burners,

said flues arranged in interconnected pairs with a partition wall therebetween, said partition wall top portion terminating below the top wall of said heating chambers to provide a passageway between said interconnected flues for the flow of waste combustion gas from the on flue into the adjacent interconnected off flue,

division walls extending transversely across said heating chambers and separating said pairs of interconnected flues,

a plurality of regenerator compartments positioned beneath said heating chambers,

regenerator pillar walls separating said regenerator compartments and providing support for said heating chambers and said coking chambers,

said high and low burners in each of said flues having vertical fuel supply passageways extending downwardly therefrom through said regenerator pillar wall to a fuel gas distribtuion system located below said regenerators,

said fuel gas distribution system arranged to supply fuel gas through said fuel supply passageways in a preselected sequence so that fuel gas is supplied to the high and low burners of the on flue,

horizontal passageways below said regenerators connecting certain of said vertical fuel supply passageways so that a first portion of the waste combustion gas flowing downwardly through said off flue is conveyed downwardly through one of said vertical fuel supply passageways in said off flue and admixed with fuel gas flowing upwardly through one of said vertical fuel supply passageways to said interconnected on flue and a second portion of the waste combustion gas flowing downwardly through said off flue is conveyed downwardly through the other of said vertical fuel supply passageways in said off flue and admixed with fuel gas flowing upwardly through one of said vertical fuel supply passageways to said adjacent on flue on the opposite side of said division wall to thereby circulate waste combustion gas between flues separated by a division wall, and each said horizontal passageway connecting the vertical fuel supply passageways to respective burners of an inverse position. 2. In a hairpin flue type high chambered horizontal coking retort oven a combination of heating elements therefor to provide uniform heating for the coking chambers comprising:

:a plurality of elongated heating chambers arranged in alternating relation with elongated coking chambers,

said heating chambers each having a plurality of vertical combustion flues arranged side by side and in a row,

said flues arranged in interconnected pairs with a partition wall therebetween, said partition wall terminating below the top of said heating chamber to provide a passageway between said interconnected flues for the flow of waste combustion gas from the on flue into the adjacent interconnected off flue,

division walls extending transversely across said heating chambers and separating said pairs of interconnected flues,

a plurality of regenerator compartments positioned beneath said heating chambers,

regenerator pillar Walls separating said regenerator compartments and providing support for said heating chambers and said coking chambers,

said flues each having a gas port adjacent the flue base portion and defining a low level positioned burner and a vertical fuel supply passageway extending downwardly from said low level burner through said regenerator pillar wall to a fuel gas distribution system located below said regenerators,

said flues each having another gas port in one of said walls spaced above said low level burner and defining a high level positioned burner and another vertical fuel supply passageway extending downwardly from said high level burner through said regenerator wall to a fuel gas distribution system located below said regenerators,

said fuel gas distribution system arranged to supply fuel gas through said fuel supply passageways in a preselected sequence so that fuel gas is supplied to the high and low level burners of the on flues,

a first horizontal passageway below the regenerators connecting the vertical fuel supply passageway for one of said burners of one of said pair of interconnected flues with the vertical fuel supply passageway for One of said burners of the other of said interconnected flues for the circulation of waste combustion gas from one of said interconnected flues to the other of said interconnected flues and for admixture with the fuel gas supplied to the on flue,

a second horizontal passageway below the regenerators connecting the vertical fuel supply passageway for the other of said burners of the first named interconnected flue with the vertical fuel supply passageway for a burner of an adjacent flue separated therefrom by a division wall to thereby circulate waste combustion gas between flues separated by a division wall for admixture with fuel gas supplied to the on flue, and

each said horizontal passageway connecting the vertical fuel supply passageways to respective burners of an inverse position.

3. In a hairpin flue type high chambered horizontal coking retort oven a combination of heating elements therefor to provide uniform heating for the coking chambers comprising;

a plurality of elongated heating chambers arranged in alternating relation with elongated coking chambers,

said heating chambers each having a plurality of vertical combustion flues arranged side by side and in a row,

said flues arranged in interconnected pairs with a partition wall therebetween, said partition wall terminating below the top of said heating chamber to provide a passageway between said interconnected flues for the flow of waste combustion gas from the on flue into the adjacent interconnected off flue,

division walls extending transversely across said heating chambers and separating said pairs of interconnected flues,

a plurality of regenerator compartments positioned beneath said heating chambers,

regenerator pillar walls sepanating said regenerator compartments and providing support for said heating chambers and said coking chambers,

said flues each having a gas port adjacent the flue base portion and defining a low level positioned burner and a vertical fuel supply passageway extending downwardly from said low level burner through said regenerator pillar wall to a fuel gas distribution system located below said regenerators,

said flues each having another gas port in one of said walls spaced above said low level burner and defining a high level positioned burner and another vertical fuel supply passageway extending downwardly from said high level burner through said regenerator wall to a fuel gas distribution system located below said regenerators,

said fuel gas distribution system arranged to supply fuel gas through said fuel supply passageways in a preselected sequence so that fuel gas is supplied to the high and low level burners of the on flues,

a first horizontal passageway below the re generator connecting said vertical fuel supply passageway for said high level burner of one of said pair of interconnected flues with said vertical fuel supply passageway for said low level burner of the other of said pair of interconnected flues for the circulation of waste combustion gas from one of said interconnected flues to the other of said interconnected flues and for admixture with the fuel gas supplied to the on flues,

a second horizontal passageway below the regenerators connecting said vertical fuel supply passageway for said low level burner of said first named flue of said pair of interconnected flues with said vertical fuel supply passageway for the high level burners of an adjacent flue separated from said first named flue by a division wall to thereby circulate waste combustion gas between flues separated by a division wall for admixture with fuel gas supplied to the on flue, and

each said horizontal passageway connecting the vertical fuel supply passageways to respective burners of an inverse position.

4. In a hairpin flue type high chambered horizontal coking retort oven a combination of heating elements therefor to provide uniform heating for the coking chambers comprising;

a plurality of elongated heating chambers arranged in interconnecting arrangement with elongated coking chambers,

said heating chambers each having a plurality of vertical combustion flues arranged side by side and in a row,

said flues arranged in interconnected pairs with a partition wall therebetween, said partition wall terminating below the top wall of said heating chamber to provide a passageway between said interconnected flues for the flow of waste combustion gas from the on flue into the adjacent interconnected off flue,

division walls extending transversely across said heating chambers and separating said pairs of interconnected flues,

a plurality of regenerator compartments positioned beneath said heating chambers,

regenerator pillar walls separating said regenerator compartments and providing support for said heating chambers and said coking chambers,

said flues each having a gas port adjacent the flue base portion and defining a low level positioned burner and a vertical fuel supply passageway extending downwardly from said low level burner through said regenerator pillar wall to a fuel gas distribution system located below said regenerators,

said flues having another gas port in said division wall spaced above said low level burner and defining a high level positioned burner and another vertical fuel supply passageway extending downwardly from said high level burner through said division wall and through said regenerator pillar wall to a fuel gas distribution system located below said regenerators,

said fuel gas distribution system arranged to supply fuel gas through said fuel supply passageways in a preselected sequence so that fuel gas is supplied to the high and low burners of the on flue,

a first horizontal passageway below the regenerators connecting the vertical fuel supply passageways for the high level burners on opposite sides of said divi sion wall for the circulation of waste combustion gas between flues separated by a division wall for admixture with fuel gas supplied to the on flue,

a second horizontal passageway below the regenerators connecting the vertical fuel supply passageways for the low level burners of a pair of interconnected flues for the circulation for waste combustion gas from one of said interconnected flues to the other of said interconnected flues and for admixture with the fuel gas supplied to the on flue, and

each said horizontal passageway connecting the vertical fuel supply passageways to respective burners of an inverse position.

5. In a hairpin flue type high chambered horizontal coking retort oven a combination of heating elements therefor to provide uniform heating for the coking chambers comprising;

a plurality of elongated heating chambers arranged in interconnecting arrangement with elongated coking chambers,

said heating chambers each having a plurality of vertical combustion flues arranged side by side and in a row,

said flues arranged in interconnected pairs with a partition wall therebetween, said partition wall top portion terminating below the top wall of said heating chambers to provide an upper passageway between said interconnected lflues for the flow of waste combustion gas from the on flue into the adjacent interconnected off flue,

said partition walls having an opening therethrough adjacent the lower portion of said heating chamber forming a lower passageway for the recirculation of a portion of the waste combustion gas from the off flue to the interconnected on flue,

division walls extending transversely across said heating chambers and separating said pairs of interconnected flues,

a plurality of regenerator compartments positioned beneath said heating chambers,

regenerator pillar walls separating said regenerator compartments and providing support for said heating chambers and said coking chambers,

said flues each having a gas port adjacent the flue base portion and defining a low level positioned burner and a vertical fuel supply passageway extending downwardly from said low level burner through said regenerator pillar wall to a fuel gas distribution system located below said regenerators,

said fiues having another gas port in said division wall spaced above said low level burner and defining a high level positioned burner and another vertical fuel supply passageway extending downwardly from said high level burner through said division wall and through said regenerator pillar wall to a fuel gas distribution system located below said regenerators,

said fuel gas distribution system arranged to supply fuel gas through said fuel supply passageways in a preselected sequence so that fuel gas is supplied to the high and low burners of the on flue, a first horizontal passageway below the regenerators connecting the vertical fuel supply passageways for the high level burners on opposite sides of said division wall for the circulation of waste combustion gas between flues separated by a division wall for admixture with fuel gas supplied to the on flue,

a second horizontal passageway below the regenerators connecting the vertical fuel supply passageways for the low level burners of a pair of interconnected flues for the circulation of waste combustion gas from one of said interconnected flues to the other of said interconnected fiues and for admixture with the fuel gas supplied to the on flue, and

each said horizontal passageway connecting the vertical fuel supply passageways to respective burners of an inverse position.

References Cited UNITED STATES PATENTS 3,123,540 3/1964- Van Ackeren 202-139 XR 3,196,086 7/1965 Wethly 202-138 XR 3,345,051 10/1967 Van Ackeren 202-439 XR NORMAN YUDKOFF, Primary Examiner. D. EDWARDS, Assistant Examiner. 

